<!DOCTYPE html>
<html>
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>document.domain - b</title>
</head>
<body>
    b
    <script>
        document.domain = 'baidu.com';
        var aa = 'FruitJ';
    </script>
</body>
</html>